Metals in Dentistry Flashcards

1
Q

Define elastic modulus.

A

A measure of a material’s ability to resist elastic deformation. Higher elastic module means more stiff.

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2
Q

Define yield strength

A

The measure of a material’s ability to resist permanent deformation.

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3
Q

Define flexural strength.

A

A measure of a material’s ability to resist fracture when bending force is applied.

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4
Q

Define compressive strength.

A

The measure of a material’s ability to resist being crushed or broken with application of a pushing force.

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5
Q

Define Tensile strength.

A

The measure of a material’s ability to resist being broken with pulling force.

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6
Q

Define creep.

A

A measure of the amount of plastic deformation of a material subjected to a compressive force over a given period of time.

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7
Q

Define elongation percent.

A

The measurement of a material’s ability to be stretched up to its breaking point.

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8
Q

Define Ductility.

A

A solid materials ability to be plastically deformed under tensile forces without fracture. Stretched into a wire.

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9
Q

Define malleability.

A

a solid material’s ability to form a thin sheet by hammering or rolling.

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10
Q

Define hardness.

A

The ability of a solid material to resist plastic deformation.

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11
Q

Define fracture toughness.

A

Material’s ability to resit fracture in presence of existing crack.

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12
Q

What is dimensional change?

A

The volumetric change that can occur when the components of a material react to form a product.

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13
Q

Define trituration.

A

To crush, grind, or pound into small particles.

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14
Q

What is the difference between an amalgam alloy and dental amalgam?

A

An amalgam alloy is a combination of solid metals. A dental amalgam is an amalgam alloy mixed with Hg.

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15
Q

What does the term eutectic refer to?

A

When a mixture of substances melt and solidify at a single temperature that is lower than the melting points of the individual parts.

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16
Q

What is the composition of Ag and Cu at the eutectic point?

A

72% Ag and 28% Cu.

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17
Q

What is the composition of Cu in admixed regular, admixed unicompositional and unicompositional?

A

Admixed regular the lathe portion has low Cu and the spherical has high Cu. Admixed unicompositional the lathe and spherical has the same amount of CU and the unicompositional is only spherical.

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18
Q

What does Cu do to an alloy?

A

Increases strength and hardness while decreasing corrosion.

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19
Q

What does Zn do to an alloy? Why is it bad?

A

Prevents oxidation during manufacturing. Is bad because when there is moisture contamination the zinc will delay expansion.

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20
Q

What does adding the Ag-Cu eutectic to the alloy do?

A

The Gamma 2 phase is replaced by the eta prime making a harder and more corrosion resistant amalgam.

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21
Q

What are some of the physical differences between admixed alloys and spherical alloys?

A

Admixed are more condensable and show less post op sensitivity. The spherical give better early strength, smoother surface, require less Hg and more retentive.

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22
Q

What are the setting times for amalgams?

A

Most will have 60% setting within 1 hour and 100% strength by hour 24.

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23
Q

What are some of the mechanical properties of dental amalgam?

A

Compressive strength, tensile strength, elastic modulus, creep.

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24
Q

What are some of the physical properties of dental amalgam?

A

dimensional change, dimensional stability, corrosion resistance, tarnish resistance.

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25
Q

What is the bonding sometimes used in amalgam fillings?

A

4-META

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26
Q

When Zn is contaminated with water, what chemical processes take place?

A

Electrolysis of water by Zn releases ZnO and H2 gas. H2 gas increases the pressure causing creep and expansion.

27
Q

What metal causes amalgam restorations to be cathodic?

A

High Cu.

28
Q

What is the benefit of the corrosion products of an amalgam restoration?

A

They help fill the micro-gap at the margin.

29
Q

What are the sizes of a 1, 2, and 3 spill?

A

1- 400 mg. 2- 600 mg. 3- 800 mg.

30
Q

What is Coombs type IV hypersensitivity?

A

Also known as contact dermatitis.

31
Q

What is lichenoid reaction?

A

Also known as lichen planus and is an allergic reaction to amalgam of the oral tissues.

32
Q

What is the greatest toxicity concern with dental amalgams?

A

Inhalation.

33
Q

What are the three forms of Hg?

A

Elemental released into air with fossil fuels. Inorganic found in the environment. Organic found in soil and water. This form is the most insidious.

34
Q

What dental material is an estrogen mimicker?

A

Bisphenol A.

35
Q

What is the difference between noble metals and base metals?

A

Nobel metals retain their surface luster in dry air and resist oxidation. Base metals do not retain their surface luster and oxidize.

36
Q

What does Iridium, Ruthenium, and Rhodium do to casting?

A

Act as nucleating centers for molten metal as it cools.

37
Q

Type I - Type IV noble casting allows has what grading system?

A

Type I is soft and type IV extra hard.

38
Q

What are some of the requirements of ceramo-metal alloys?

A

Must have a melting temperature substantially higher then the firing temperature of the ceramic. Must also create metal oxides to help bond ceramic and metal. Must have a high sag resistance.

39
Q

What are some of the uses of base metal alloys in dentistry?

A

Removable partial denture. Endodontic instruments. Orthodontics. Implants.

40
Q

Define metalloid.

A

have properties of both metal and non-metal.

41
Q

What are some examples of base metals?

A

Nickel and Beryllium.

42
Q

What does Be do in a metal alloy cast?

A

Improves castability by decreasing alloy’s melting temp and increasing porcelain metal bond.

43
Q

What is the benefit of nickel in metal alloy cast?

A

Increases elastic modulus, strength and hardness.

44
Q

What makes up the Gamma 1 and gamma 2 phases?

A

Gamma 1 is AgHg and Gamma 2 is SnHg.

45
Q

What is Vitallium and Ticonium often used for in dentistry?

A

RPD frameworks.

46
Q

What is Rexillium II often used for in dentistry?

A

PFM metals.

47
Q

What are some of the characteristics of base metal alloys when compared to noble metal alloys?

A

Have higher hardness, elastic modulus, are more difficult to cast and undergo more shrinkage.

48
Q

Which has a higher melting range, Base metal alloys or cast noble?

A

Base metal alloys.

49
Q

What does the pre-oxidation of metals alloys achieve?

A

Relieves internal stresses and form oxide layer for porcelain to bond to.

50
Q

What are some of the benefits of titanium?

A

High strength/density ratio, immunologically inert, resistant to electrochemical degradation, and high corrosion resistance.

51
Q

What does passivate mean?

A

The ability of a material to form an oxide layer at its surface making it unreactive.

52
Q

What are the molecules that have profound effects on mechanical and physical properties of titanium?

A

Oxygen and Iron.

53
Q

What is allotropy?

A

The ability of some elements to exist in two or more different forms in the same physical state. Seen in titanium.

54
Q

What is the alpha phase of titanium?

A

Hexagonal close-packed crystal lattice.

55
Q

What is the beta phase of titanium?

A

Body-centered cubic form.

56
Q

What is a wrought alloy?

A

A metal that is shaded by hammering.

57
Q

What is meant by cold working metal?

A

Heating the metal and hammering it out. Note that it is not in liquid state but still heated.

58
Q

What does cold working a metal increase?

A

The tensile strength and hardness.

59
Q

What can happen to prolonged heating of wrought forms?

A

Can cause them to recrystallize and become brittle.

60
Q

What is one of the important characteristics of Nitinol?

A

It has super-elasticity.

61
Q

What is steel?

A

Iron alloyed with carbon.

62
Q

What does carbon do to steal?

A

Gives it strength but also makes is more brittle.

63
Q

What is stainless steel?

A

A steel that contains a minimum of 11% Cr.

64
Q

What are the three major stainless steels?

A

Martensitic (hardenable by heat), ferritic (magnetic, cant harden) and austentitic (most corrosion resistant).